The v10 throws are 72 degrees apart, not 90. The Viper V10 with its 90 degree block and odd fire configuration is inherently balanced. To alter any of those items would result in an unbalanced engine, and require a balance shaft adding complexity. The Lambo V10 is a good example. It is a 90 degree block like the Viper, but even fire as you are technically talking about. It is unbalanced and requires a balance shaft. The only way around this would be to run a 72 degree block, but that changes center of gravity and engine package size, not to mention the design of just about everything else.
